what is the process that allows a player to bounce the balls in?

[scottycoyote]

im sure youve seen it and done it........you shoot a long straight in shot into the corner, the object ball hitsseveral inches up the rail and still bounces in, im not talking a slowrolled shot either. Ive seen efren do this on tv alot too. Its like a certain looseness of stroke allows it, where a stiffer shot would have completely richocheted out........just wondering if anyone knows the physics behind this or is it just one of those things.

 

[Schmohawk]

im sure youve seen it and done it........you shoot a long straight in shot into the corner, the object ball hitsseveral inches up the rail and still bounces in, im not talking a slowrolled shot either. Ive seen efren do this on tv alot too. Its like a certain looseness of stroke allows it, where a stiffer shot would have completely richocheted out........just wondering if anyone knows the physics behind this or is it just one of those things.

Yep_You just loosen that wrist and aim for diamond number 2.

 

[Varney Cues]

Its something known as "pocket speed" used with no english, so the ball doesn't jump when it contacts the rail.

 

[scottycoyote]

no I dont mean pocket speed......youre shooting the ball fairly hard and it just flies in the pocket, almost like the ball has english on it and hits one of the points of the pocket and just spins in, but you didnt shoot it like that.

 

[mikepage]

no I dont mean pocket speed......youre shooting the ball fairly hard and it just flies in the pocket, almost like the ball has english on it and hits one of the points of the pocket and just spins in, but you didnt shoot it like that.

I think you're just seeing pocket facings that allow for this. When the pockets narrow on the way in, these shots get rejected. When they are more parallel, these shots are accepted.

Cueballs sometimes have "get-in english." We've all seen it: that sinking feeling our cueball is headed for the pocket, only to feel relieved when we realize it's going to miss by a bit. Then the horror returns when we see the get-in spin on the cueball.

Some people talk about get-in english on the object ball that they purposefully transfer from the cueball--say on down-the-rail shots. Those people are dreaming, imo.

mike page
fargo

 

[MFelsen]

First of all i believe it`s a question on what kind of table you are playin`.

On some of them this shot will work, on others not. It depends on the pocketcut.

When it´s more open it is easier to pocket an ball like you explained.

Tables with small pocketcuts won`t forgive you and reject the shot and thow it back of the pocket.

But i could imagine, that "get-in english" might be a good choice pocketing those balls, because the throw back effect gets a little bit smaller.

So your percentage of pocketing will rise.

 

[Colin Colenso]

The pocket only knows the position the OB hits it, the angle it's coming from, the speed and the spin.

Loosening up the wrist won't create any variables that will affect the shot, unless it reduces speed.

Often pockets on TV look more generous than they seem when playing on them. This may be due to the parralex error on certain shots which makes the angle of incidence to rail look greater than it actually is.

Also, TV tables usually have very new cloth, which tends to slide more on the rails and into the pockets. I reckon a 4.5" pocket with new cloth plays similar to a 4.8" pocket with worn grippy cloth.

 

[Andrew Manning]

Try this shot, with just the CB, at the speed you're talking about. Try to hit the same point on the long rail before the pocket, with both right and left english.

CueTable Help

As I've diagrammed it, right english should make it much easier to pocket the ball, for two reasons. One is the right english should throw the ball to the right (deeper into the pocket) when it hits the far pocket facing. The other is that the ball seems to "skim" the rail more lightly with reverse English at a shallow angle like this. The running english (left in this case) almost seems to make it grab the rail and throw itself away, whereas the reverse english seems to make it brush the rail and not kick away from the rail nearly as much.

I think the physics behind this have to do with static vs. kinetic friction, which is the concept that two surfaces moving against each other don't experience as much frinction as those same two surfaces sitting still against each other. Right english in my diagram means the right side of the ball is moving very fast with respect to the rail since the spin and the translational movement are the same direction (additive) on that side of the ball. This means that when contact with the rail is made, the ball keeps sliding against the rail, never "gripping". In the opposite case of left english, the right side of the ball is moving slower, because the rotation is working against the direction of translational movement. So when contact with the rail is made, I think the cloth, especially if it's older and slower cloth, is able to grip the surface of the ball, and this "grip" pulls the front of the ball into the rail harder, compressing it more, and kicking the ball further out.

Any of that make sense? It's all just me trying to imagine what's really going on to explain what I've seen empirically; i.e. that running english causes the ball to kick away from a glancing contact with the rail more than reverse english.

-Andrew

 

[Andrew Manning]

Try this shot, with just the CB, at the speed you're talking about. Try to hit the same point on the long rail before the pocket, with both right and left english...

Sorry, I forgot to get to the point of that last post, which is to say that the object ball often has some noticeable sidespin component to its rotation, either by transferred english from very full hits, or cut-induced spin from cut shots. This is evident on bank shots, where good bankers know how to lengthen and shorten the angles off the rail using object ball sidepsin. The spin can work for you or against you if you graze that rail. That was the point of the long-winded explanation there.

-Andrew

 

[Andrew Manning]

Bumping because I'm interested to hear more opinions on this topic.

-Andrew

 

[Aaron_S]

You can sometimes see the effects of "get-in spin" (or "go-in spin" as I've always called it) on shots like this.

CueTable Help

Cutting the 1-ball puts a slight bit of right-hand spin on it, which, depending on the table, may make the difference between a make or a miss on this shot. Add a little left to the cb, and you get a little more go-in spin on the 1. Older Gold Crowns stick out in my mind as being one of the tables where this can make a difference. Something about those pockets makes it possible to cut balls into the side from ungodly angles, although I've always been better at scratching in the side from ungodly angles.

Good luck!

 

[Jal]

...Any of that make sense? It's all just me trying to imagine what's really going on to explain what I've seen empirically; i.e. that running english causes the ball to kick away from a glancing contact with the rail more than reverse english.

Andrew, some ideas.

Theory #1

It doesn't really happen. When you try this you're not paying much attention to squirt so that you get more of a glancing angle with reverse english.

Contra Theory #1: After 2,687,543,232 posts on deflection over the years, nobody knows how much a cue actually squirts. At least there is no consensus. But of course, they do squirt some, for sure.

Theory #2

Just like with ball/ball throw, the coefficient of friction diminishes with large relative surface speeds. According to this view, as with ball/ball throw, a moderate amount of running english would increase the coefficient and thus the shortening of the angle off the rail. Maximum shortening would occur when the ball just reaches a rolling state across the cushion at the end of contact (or something like that). Still more running english would reduce the shortening by bringing the ball to a rolling state quicker.

So, a lot of reverse versus a small amount of running might result in a relative lengthening of the rebound angle.

Contra Theory #2: I've read a paper where the ball/cloth friction coefficient was measured as a function of surface speed. Apparently, it remains fairly constant over a wide range of speeds, but then begins diminishing when the speed drops below some value - the opposite of ball/ball friction.

Theory #3

As you say, maybe some static 'grabbing" of the cushion might be taking place.

Contra Theory #3: If the ball reaches a rolling state across the cushion, without considering anything else (bed friction), the friction with the cushion should be reduced to zero for all practical purposes. However, there is bed friction to contend with. It wants to slow the ball down, while the spin against the cushion tries to maintain its speed. The net effect, according to my figuring, is that once the ball achieves rolling, it will be slowed further by 5/7 of the amount it would have been slowed by bed friction if the cushion wasn't helping to maintain its speed. This is a small effect since bed friction is small compared to cushion friction. Ergo, running english should lenghten the rebound angle, relatively speaking.

Contra Contra Theory #3: Bed friction also provides a torque which alters the forces along the cushion as they provide a counte-torque. That may invalidate, in part, Contra Theory # 3.

Theory #4

It's swerve, or masse' if you like. Because of the cushions nose height, the spin picked up by the ball while in contact causes it to curve away from the cushion, shortening the rebound angle. In the case of a grazing incoming angle, enough original spin is retained to either supplement this (running english), or oppose it (reverse english). We're assuming a non-level stick.

Contra Theory #4: Not sure if enough of the relevant spin component can be retained.

Jim

 

[Andrew Manning]

Jim,

Having thought about it more, here's where I was trying to go with the friction angle:

Tennis serves don't bounce as high on grass as they do on clay, especially in morning matches on grass that has residual dew moisture. It makes them hard to return, and the way tennis players describe it is that the ball skids instead of bouncing on the grass. Part of a tennis ball's bounce is caused by friction with the ground. Visualize: as the bottom of the ball hits the ground, friction creates topspin, meaning the leading edge of the ball is pulled down toward the ground. This "pulling down" of the leading edge of the ball compresses it into the ground more firmly, causing more bounce.

I think the same thing happens with a CB against a rail, particularly with newer cloth on the rail. Reverse english, as you mentioned in theory #2, decreases the coefficient of friction with the rail, and causes "skidding" instead of bouncing. Running english however, has that same tennis ball effect of making the leading edge of the ball pull into the rail, compressing it more, and getting more bounce. I think that's why I've observed running english to shorten the angle more; because it produces more bounce off the rail; whereas reverse will skim the rail and not bounce much.

Any thoughts on that phrasing of the idea?

-Andrew

 

[stroke]

im sure youve seen it and done it........you shoot a long straight in shot into the corner, the object ball hitsseveral inches up the rail and still bounces in, im not talking a slowrolled shot either. Ive seen efren do this on tv alot too. Its like a certain looseness of stroke allows it, where a stiffer shot would have completely richocheted out........just wondering if anyone knows the physics behind this or is it just one of those things.

I see it all the time, even on tables with "tight" pockets. I believe that it happens most often when the ball has reverse english and hits the rail at a shallow angle. The english reduces the angle further AND when it hits the pocket facing, the english pushes it into the pocket rather than rattle it.

 

[scottycoyote]

thanks guys, good stuff

I was interested in this because last night i was shooting with a glove and i noticed i bounced in several shots that to me shouldnt have even gone......no english involved. It didnt make sense to me, how or even if a glove could have any type of effect in this.........my stroke feels alot looser and balls are bouncing in, just trying to understand.

 

[Andrew Manning]

thanks guys, good stuff

I was interested in this because last night i was shooting with a glove and i noticed i bounced in several shots that to me shouldnt have even gone......no english involved. It didnt make sense to me, how or even if a glove could have any type of effect in this.........my stroke feels alot looser and balls are bouncing in, just trying to understand.

Was it a newer cloth than you're used to? Perhaps a different pocket cut?

If you're referring to cut shots down the rail, using stun rather than top or bottom would put more "reverse english" on the OB, according to Colin Colenso's studies in cut-induced-throw. Perhaps your looser stroke was producing a better stun.

Or perhaps you had perviously been in the habit of putting outside english on your cut shots, and consciously or unconsciously stopped doing it because of your new-found confidence in your stroke. The outside english would have been putting running spin or no spin on the OB, and changing that to center ball or inside english would put that reverse spin which seems to make them get in easier.

Or perhaps without realizing it, your looser stroke meant you weren't forcing the CB around as much, and you were actually hitting your shots slower. This would increase the "good" OB spin while decreasing speed, and slower speed give the ball lass chance of rattling.

If you're hitting shots at the same speed, same english, on the same table, cloth, and rails as before, the stroke itself has no power to decide whether the ball rattles or drops.

-Andrew

 

[jsp]

CueTable Help

I think it's mostly about how much natural roll the OB has when it hits the rail.

If you hit the 1 and the 8 with exactly the same speed and at exactly the same line, i'll bet that you'll pocket the 8 more times than the 1. The 1 ball won't acquire all its rolling english when it hits the rail. However, the 8 has more than enough room to achieve full roll when it hits the cushion. The more roll, the higher the surface speeds, the lesser the ball-cloth friction, and the shallower the rebonding angle.

Try it. I'm sure the further the OB is away from the pocket, the more likely you'll "bounce the balls in". Just my guess.

 

[Colin Colenso]

Jim,

Having thought about it more, here's where I was trying to go with the friction angle:

Tennis serves don't bounce as high on grass as they do on clay, especially in morning matches on grass that has residual dew moisture. It makes them hard to return, and the way tennis players describe it is that the ball skids instead of bouncing on the grass. Part of a tennis ball's bounce is caused by friction with the ground. Visualize: as the bottom of the ball hits the ground, friction creates topspin, meaning the leading edge of the ball is pulled down toward the ground. This "pulling down" of the leading edge of the ball compresses it into the ground more firmly, causing more bounce.

I think the same thing happens with a CB against a rail, particularly with newer cloth on the rail. Reverse english, as you mentioned in theory #2, decreases the coefficient of friction with the rail, and causes "skidding" instead of bouncing. Running english however, has that same tennis ball effect of making the leading edge of the ball pull into the rail, compressing it more, and getting more bounce. I think that's why I've observed running english to shorten the angle more; because it produces more bounce off the rail; whereas reverse will skim the rail and not bounce much.

Any thoughts on that phrasing of the idea?

-Andrew

Andrew,
You may have a point here. On sliding rails I think I have observed shots with reverse english sliding off the rail more than with running english on narrow angles of incidence, but it could be partly an illusion.

In tennis the kick (high bounce) serve is played with topspin, the equivalent of running english. But this may be mostly due to the 'magnus effect' which causes topspin to curve the ball downward at a steeper angle, due to aerodynamic effects.

btw: I have wondered how much the magnus effect could contribute to CB swerve with side english. Probably not much, but it could be significant on firmer shots over distance. Right english would swerve the CB left, giving the appearance of increased squirt.

Colin

 

[Andrew Manning]

Andrew,
You may have a point here. On sliding rails I think I have observed shots with reverse english sliding off the rail more than with running english on narrow angles of incidence, but it could be partly an illusion.

In tennis the kick (high bounce) serve is played with topspin, the equivalent of running english. But this may be mostly due to the 'magnus effect' which causes topspin to curve the ball downward at a steeper angle, due to aerodynamic effects.

btw: I have wondered how much the magnus effect could contribute to CB swerve with side english. Probably not much, but it could be significant on firmer shots over distance. Right english would swerve the CB left, giving the appearance of increased squirt.

Colin

The "magnus effect" is entirely due to air resistance, no? I would say that the density and surface smoothness of a billiard ball make it almost impervious to air resistance at the speeds it travels on a pool table, so I'd guess the magnus effect doesn't contribute any measurable amount.

-Andrew

 

[Jal]

Jim,

Having thought about it more, here's where I was trying to go with the friction angle:

Tennis serves don't bounce as high on grass as they do on clay, especially in morning matches on grass that has residual dew moisture. It makes them hard to return, and the way tennis players describe it is that the ball skids instead of bouncing on the grass. Part of a tennis ball's bounce is caused by friction with the ground. Visualize: as the bottom of the ball hits the ground, friction creates topspin, meaning the leading edge of the ball is pulled down toward the ground. This "pulling down" of the leading edge of the ball compresses it into the ground more firmly, causing more bounce.

I think the same thing happens with a CB against a rail, particularly with newer cloth on the rail. Reverse english, as you mentioned in theory #2, decreases the coefficient of friction with the rail, and causes "skidding" instead of bouncing. Running english however, has that same tennis ball effect of making the leading edge of the ball pull into the rail, compressing it more, and getting more bounce. I think that's why I've observed running english to shorten the angle more; because it produces more bounce off the rail; whereas reverse will skim the rail and not bounce much.

Any thoughts on that phrasing of the idea?

-Andrew

Andrew,

It could be a lack of imagination on my part, but I don't see the mechanism you're describing in play. In a vacuum, the tennis ball should bounce up to the same height in both cases, with the caveat that the different friction should cause some differences in the arrangement of internal stresses, which might affect the coefficient of restitution. In order to posit more compression for the higher friction case, I think you'd have to show that some component of the friction is directed downward. I don't see that happening, but maybe you're seeing something I'm not. Please expand on this if you're convinced it's true.

As far as the friction being reduced with greater surface speed, I can only point here:

http://www.engr.colostate.edu/~dga/pool/physics/witters.pdf

They don't say what type of cloth they used, or I just can't find it.

If the above is generally true across different cloths, I do believe running english should result in a considerable reduction in the slowing down of the ball in the parallel direction over the reverse english case, ie, lengthening the rebound angle, both because the ball reaches a rolling state on the cushion and because of the reduction in the friction coefficent. The former is the most important factor. How much reduction takes place depends on how much english is used. Friction in the relevant direction can be nearly zero throughout impact if the initial spin is just right.

So, if the ball does in fact rebound shorter with running in some cases, I'm leaning toward the swerve idea.

Jim